Technical Field
The present invention relates to a liquid droplet discharging head and an image forming apparatus.
Description of the Related Art
Image forming apparatuses are known which include a plurality of pressure generating chambers to communicate with a plurality of discharging orifices and apply a pressure to liquid, a common liquid supplying chamber to accommodate the liquid to be supplied to these pressure generating chambers, and a plurality of individual supplying paths which individually communicates the pressure generating chambers with the common liquid supplying chamber.
For example, an inkjet head operating as a liquid droplet discharging head includes a plurality of nozzle holes serving as discharging orifices and a plurality of cavity chambers serving as pressure generating chambers which individually communicate with the nozzles to apply a pressure to ink as liquid. In addition, the inkjet head further includes an ink manifold serving as a common liquid supplying chamber to accommodate ink to be supplied to the cavity chambers and a plurality of individual supplying paths which individually communicates the cavity chambers with the manifold. Moreover, the inkjet head also includes vibration plates constituting part of the inside wall of the cavity chambers or the ink manifold. Of all the areas of the vibration plates along the plane direction, the areas forming the inside wall of the cavity chambers increase or decrease the pressure to the ink in the cavity chambers according to the vibration of the vibration plate. In addition, of all the areas, the areas forming the inside wall of the ink manifold serve as a damper portion which is displaced according to the pressure change of the ink in the ink manifold.
As the ink in the cavity chambers is pressurized by the drive of a piezoelectric element, the ink is discharged as a form of ink droplets from a nozzle hole, part of which communicates with the cavity chamber. At this time, part of the ink in the individual supplying path communicating with the cavity chamber moves back from the individual supplying path to the ink manifold to pressurize the ink in the manifold. As the pressurization to the ink in the cavity chamber ceases when the drive of the piezoelectric element stops, the pressure of the ink in the cavity chamber is back to the original value. At this time, if the ink in the ink manifold under pressure rushes back to the individual supplying path as reflective wave, the pressure of the ink in the cavity chamber takes a long time to be back. The damper portion is displaced to the direction in which the volume of the ink manifold increases when the ink in the individual supplying paths moves back to the ink manifold at the time of drive of the piezoelectric element. This is said to make it possible to reduce the rush of the reflective wave.
However, to displace the damper portion in response to slight pressure changes of the ink in the ink manifold in this inkjet head, the thickness of the damper portion is required to be extremely thin. This leads to a problem that the damper portion is easily broken because the mechanical strength is decreased.